Given that the ECJ have already ruled that Ryanair can keep their shareholding, I'd say they'll have grounds for appeal.
Grounds for completely ignoring as EU law trancends national laws.
Attempt by UK to force 2 companies headquartered and registered in another country will be interesting, it allows any 3rd country to do the same to UK companies.
This will not be lost on UK companies who will then see German courts intervening in UK companies using UKs own precedence.